The present invention relates to an anterior cervical plate, and in particular it relates to such a plate with a new and improved H-shaped design.
Anterior cervical plates and their applications are known in the art. Such plates can be attached to the anterior of two or more cervical vertebrae for the purpose of immobilizing, stabilizing, and/or aligning those vertebrae. The plates can be used for a variety of conditions, including for example, providing added strength and rigidity.
The cervical region of the spine is one of the most delicate regions in which to attach a bone plate. The vertebrae of the cervical spine are smaller than the vertebrae located in the thoracic, lumbar, and sacral regions. A spine surgeon who is inserting an anterior cervical plate has exposure to cervical vertebrae C2, down to the cervico-thoracic junction. In this region of the spine, there is less intervertebral disk space between the vertebrae.
An anterior cervical discectomy is the most common surgical procedure to treat damaged intervertebral discs in the delicate cervical region. Anterior access allows the surgeon to remove an entire intervertebral disc, which is not possible during posterior or lateral surgery. Furthermore, spine surgeons often prefer anterior insertion of a bone plate because it provides good access to the spine through a relatively uncomplicated pathway.
The goal of a discectomy is to relieve pressure on nerve roots or on the spinal cord by removing a ruptured intervertebral disc. In this procedure, the cervical spine is reached through a small incision in the front of the neck. During the surgery, the soft tissues of the neck are separated and the disc is removed. In some procedures the resulting space between the vertebrae are left open. However, in order to maintain the normal height of the disc space, the surgeon may choose to fill the space with a bone graft and utilize a plate attached to the anterior faces of the vertebrae. A bone graft can be a small piece of bone, either taken from the patient's body (often the pelvic area) or from a bone bank. This piece of bone fills the disc space and ideally will join or fuse the vertebrae together.
Cervical plates of the present type are generally elongate as to span the distance between two or more vertebrae, as required by a particular application. The plates are generally curved transversely to the spine axis so as to fit the curvature of the vertebrae to which they are attached. Additionally, plates of this type are generally concave longitudinally along the spine axis to match the curvature of the cervical spine.
Cervical plates are provided with openings for receiving bone screws. Typically, cervical plates are secured to adjacent vertebrae by bone screws which pass through openings in the cervical plate. Screw locking systems are provided to keep the vertebral screws from backing out of the plate. In the present invention, each opening in the plate has grooves or recesses for receiving a split ring, though any other suitable screw locking systems may be used. Split rings can be pre-assembled to the bone plate. A split-ring can be sized to expand upon insertion of a bone screw into an opening in the bone plate. Once the head of the screw has passed through the split ring, the split ring can contract under its natural spring tension. When the ring relaxes to its unexpanded state, it prevents the bone screw from backing out of the plate by the engagement of an undersurface of the split-ring and an upwardly facing surface on the bone screw. U.S. Pat. No. 6,602,255, titled “BONE SCREW RETAINING SYSTEM” and issued on Aug. 5, 2003 and U.S. Pat. No. 6,261,291, titled “Orthopedic Implant Assembly” and issued on Jul. 17, 2001, both disclose devices used for securing bone screws to a bone plate and are incorporated herein by reference in their entirety as if fully set forth herein.
Notwithstanding the development of the prior art to date, a need exists for an improved anterior cervical plate having a structure for maintaining or positioning bone graft or other devices in the intervertebral space, providing torsional resistance and avoiding interference with the esophagus.